Cylinder head connection for reciprocable piston internal combustion engines

ABSTRACT

A reciprocable piston internal combustion engine having one or more rows of cylinders with individual cylinder heads, in which two adjacent cylinder heads are by expandable screw bolts clamped to the pertaining cylinders and the crank case so that one or more expandable screw bolts common to two adjacent cylinder heads connects or connect two adjacent cylinder heads through a bridge with the crank case.

Unlted States Patent 1 3,699,852

Howe Oct. 24, 1972 [54] CYLINDER HEAD CONNECTION FOR [56] ReferencesCited RECIPROCABLE PISTON INTERNAL COMBUSTION ENGINES FOREIGN PATENTS ORAPPLICATIONS 934,827 11/1955 Germany [72] Inventor. Hans-Ulrich Howe,Bensberg-Frankenforst Germany 736,446 9/ 1955 Great Britain [73]Assignee: Klockner-Humboldt-Deutz Aktien- Primary Examiner-Edgar W.Geoghegan gesellschaft, Koln-Deutz, Germany Assistant Examiner-BarryGrossman [22] Filed: Dec. 8, 1970 Attorney-Walter Becker [21] Appl. No.:96,087 [57] ABSTRACT A reciprocable piston internal combustion enginehav- [30] Foreign Application Priority Data ing one or more rows ofcylinders with individual cylinder heads, in which two adjacent cylinderheads 1969 Germany 19 61 804'3 are by expandable screw bolts clamped tothe pertaining cylinders and the crank case so that one or more [52] US.Cl 92/ 169 expandable Screw bolts common to two adjacent [5 IIIt. CI. 1yli d h d connects or connect t dj t [58] Field of Search ..92/l69, 171,128, 146;

123/193 H, 193 CH; 292/256.71, 256.73

cylinder heads through a bridge with the crank case.

9 Claims, 4 Drawing Figures PATENTEUUBT 24 I972 SHEET 2 [IF 3 FIG. 2

CYLINDER HEAD CONNECTION FOR RECIPROCABLE PISTON INTERNAL COMBUSTIONENGINES The present invention relates to a cylinder head connection fora reciprocable piston internal combustion engine in which the cylindersmay be arranged in series or may be designed in V-arrangement withindividual cylinder heads, according to which two adjacent cylinderheads are by tie rods connected to the cylinder and the crank-case.

With cylinder heads of reciprocable piston engines it is a well knownfact that with increasing thermal and mechanical load, problems as tostrength and deformation arise which put a limit to a further increasein the load and thereby to a further increase in the power of theengine. This limit is inherent to the limitations of the materialemployed. With light metal cylinder heads of air-cooled internalcombustion engines, the limit of the strength of the respective materialis further decreased by the construction necessary in order toaccommodate the cooling system. In this connection, the arrangement ofthe connecting screws in the cylinder head is particularly difficultbecause the forces exerted by the screws connecting the cylinder head tothe cylinder and the crank-case bring about considerable deformations.

It is known to arrange the connecting screws for the cylinder head,depending on the number of screws either all of them or some of them, inthe locally widened separating gap between two cylinder units and toConnect both cylinder heads through a disc or link simultaneously withthe crank-case. In this connection it is disadvantageous thatdifferences in height caused by manufacturing tolerances between twocylinder units will not be compensated for so that a high end pressureand additional stresses in the screws occur as a result of bendingstresses.

It is furthermore known to convey screw forces through a crowned orspherical disc with corresponding counter bearings. Such an arrangement,however, has the drawback that the screw forces engage the marginal areaof or in the vicinity of the cylinder head whereby, caused by the shapeof the surfaces along which the cylinder head and the cylinder engageeach other, a tilting moment occurs which tilts the cylinder head whenunilaterally loosening the connecting screws. In this way the advantageof a facilitated assembly and disassembly of individual Cylinder unitsis lost because all screws have to be loosened.

Finally, an air-cooled internal combustion engine has become known asdisclosed, for instance, in German Pat. No. 940,075 and MotortechnischeZeitschrift 1968, Issue 4, Page 132-138, according to which theconnection of the cylinder head is effected by means of expandable ornecked-down bolts partially arranged in the gas passages. Such a designhas the drawback that the arrangement of the screws and the shape of thepassages have to be selected in accordance with each other even thoughthe shape of the inlet passage is determined primarily by therequirement to impart a twist upon the air flowing into the cylinder. Onthe other hand, the screw support is arranged approximately at the levelof the bottom of the cylinder head the structural height of which willin most instances with increasing thermal load of the engine not besufficient to absorb the bending moment caused by the screw forces. Adeformation will result, especially in the region of the exhaustpassages, which deformation will after a certain temperature has beenreached result in permanent deformations. A decrease in the screw forcesin the seal between the cylinder head and cylinder is the result.

It is, therefore, an object of the present invention so to design thescrew connection of cylinder heads that this connection will have only aminor influence upon the location and shape of the gas passages whilethe screw force will as far as possible be directly conveyed to theabutting or pressure surfaces between the cylinder head and thecylinder.

This object and other objects and advantages of the invention willappear more clearly from the following specification in connection withthe accompanying drawings, in which:

FIG. 1 illustrates a longitudinal section through a portion of anair-cooled internal combustion engine while two cylinders in uprightposition are shown in view.

FIG. 2 shows the two cylinder units of FIG. 1 as seen from the top anddesigned according to the invention.

FIG. 3 is a section through the two cylinder units, said section beingtaken along the line III-III of FIG. 1.

FIG. 4 shows the sealing surface of the two cylinder units of FIG. 1between cylinder head and cylinder and also the location of theexpandable screws and the points of support of the bridge.

The cylinder head connection according to the present invention ischaracterized primarily in that each two adjacent cylinder heads are byone or more expandable screws or necked-down bolts together connected tothe crank-case by means of a bridge. In this way the arrangement of thegas changing passages (inlet and outlet passages) is substantiallyindependent of the location of the screw or the screws. In view of thefact that the point of attack of the force of the bridge is located at ahigh level, the distribution of the pressure in the cylinder headbecomes more favorable and the pressing force at the joint surfacesbecomes more uniform. Moreover, the supporting points of the bridge arelocated almost vertically over the center of gravity of the fourth ofthe joint surface (Viertel- Fuegeflaeche) between the cylinder head andthe cylinder, whereby the bending moment introduced by the screw forcewill be low and a tilting moment will be prevented when two expandablescrews are unilaterally loosened.

According to a further development of the invention, auxiliary supportsare employed at the end cylinders as counter bearings for the bridges.These auxiliary supports may, with air-cooled engines, preferably be inthe form of locally reinforced jackets for the cooling air.

According to a still further development of the invention, it issuggested to convey the screw forces conveyed by the bridge to thecylinder head through the intervention of crowned or spherical pressuresurfaces and intermediate layers or shims according to the surfacepressure, said intermediate layers being plane or concave. The crownedor spherical pressure surfaces compensate for differences in the heightof the bridge support, whereas the intermediate layers compensate fordisplacements in all directions so that the requirements with regard tothe precision of the location of two cylinder units are not very high.In order to obtain a more favorable flow of the forces of the screws,especially to bring about the formation of a pressure cone which will asuniformly as possible distribute the forces over the joint surface, itis suggested that the supporting points for the bridge on the cylinderhead are spaced as far as possible from the joint surface and arepossibly arranged on the bottom of the upper cylinder head. For purposesof conveying the pressure forces from the bridge support to the jointsurface, there are preferably employed the walls of the gas changingpassages or supporting walls, fins, ribs, and reinforcements while suchreinforcements are designed in conformity with aerodynamic principles.

A further very simple design is obtained in view of precast chambers forthe expandable screws in the cylinder and the cylinder head and, morespecifically, in the form of a longitudinal groove which is sodimensioned that the flow of cooling air when passing through theseparating gap will not undergo any material throttling in view of thescrew shank.

For purposes of limiting the overall height of the engine, theconnecting elements are preferably so arranged that they are locatedwithin the greatest structural height of the internal combustion engineas it is formed by the hood for the cylinder head.

Referring now to the drawings in detail, FIG. 1 shows two cylinders 1, 2with cylinder heads 3, 4 according to which the cylinders 1, 2 are bymeans of expandable screws 5 connected to the crank-case 8 through theintervention of bridges 6 and intermediate layers or shims 7. On theoutside of the cylinder units 1, 3 2, 4 the screw force is conveyed onone hand to the cylinder heads 3, 4 and on the other hand to the jackets9, 10 for the cooling air, said jackets forming auxiliary supports.

According to FIG. 2, the cylinder heads 3, 4 are by means of expandablescrews 5 connected to the crankcase (not shown) through the interventionof bridges 6 and intermediate layers or shims 7. On the outside of thecylinder heads 3, 4, the screw force is conveyed to the auxiliarysupports forming the jackets 9, 10.

According to FIG. 3, the cylinder heads 3, 4 are at the level of the gaschanging passages 11, 12-13, 14 sectioned in a direction transverse tothe cylinder axis. The advantageous arrangement 'of the expandablescrews 5 in the separating gap between two cylinder units illustratesthe flexibility the designer has for designing the gas changingpassages, preferably the inlet passages l l, 13, and also shows thefavorable design of the fins at the very hot inner parts of cylinderhead cover means 20 of the cylinder head. The direction of flow of thecooling air is indicated by arrows. The free chambers 15 for theexpandable screws 5 form passages of sufficiently large dimensions forthe cooling air.

FIG. 4 illustrates the joint surfaces 16 of the cylinder heads and thecylinders with their surface central lines 18. The screw forces conveyedby means of bridges are at the points 17 where the forces attack,conveyed to the cylinder head. The connecting lines 19 of the points 17intersect the central line 18 of the joint surface 16. As a resultthereof, a tilting of the cylinder head in response to a unilateralloosening or tightening of the expandable screws for assembly ordisassembly purposes of the adjacent cylinder head will be prevented inan advantageous manner.

Although the illustrated example shows the points 17 located inprojection in pairs within and outside the central line 18, it is to beunderstood that the invention also includes arrangements according towhich all points 17 are located within the central line 18. Similarly,the present invention comprises designs according to which the jointsurfaces have a shape other than circular shape, whereas the points ofattack of the forces all or partially located in the projection upon thejoint surface will with an engine with the cylinders in seriesarrangement not result in any tilting moment toward the adjacentcylinder.

It is, of course, to be understood that the present invention is, by nomeans, limited to the particular showing in the drawings but alsocomprises any modifications within the scope of the appended claims.

What 1 claim is:

1. A reciprocable piston internal combustion engine, which includes: atleast two serially arranged adjoining cylinders with separatelydetachable individual cylinder heads, a crank case associated with saidcylinders, bridge means for engagement with said cylinder heads, andexpandable screw means, at least one of said screw means being common totwo adjacent cylinder heads with only said expandable screw meanstransmitting screw force by way of said bridge means upon two adjoiningcylinder heads and detachably connecting said two adjacent cylinderheads individually separable from the pertaining cylinders relative tosaid crank case.

2. An arrangement according to claim 1, in which each of said cylinderheads includes a plurality of bridge support points, and in which thevertical projection of the connecting line of two adjacent bridgesupport points defines a chord with regard to the surface center line ofthe annular joint surface between a cylinder head and the pertainingcylinder.

3. An arrangement according to claim 1, which includes auxiliarysupporting means arranged at the cylinders at the ends of said engineand forming counter bearings for the respective adjacent bridge means.

4. An arrangement according to claim 1, in which said bridge means areprovided with crowned engaging surfaces facing the respective adjacentcylinder head, and in which shim means are interposed between saidcrowned engaging surfaces and the pertaining adjacent cylinder headsurfaces.

5. An arrangement according to claim 2, in which said bridge supportpoints of said bridge means are located on the upper surface of thepertaining cylinder head and are spaced from said joint surface as faras possible.

6. An arrangement according to claim 2, in which said engine has gasinlet and outlet passage means, and in which said bridge support pointsare so located that the forces introduced into the cylinder beads bysaid bridge means pass through the walls defining said inlet and outletpassage means.

7. An arrangement according to claim 2, in which said engine hasreinforcing wall means, and in which said bridge support points are solocated that the forces introduced into the cylinder heads by saidbridge means pass through said reinforcing wall means.

cylinder heads, and in which said expandable screw means with saidbridge means are located within the maximum structural height of theengine including said cylinder head cover means

1. A reciprocable piston internal combustion engine, which includes: atleast two serially arranged adjOining cylinders with separatelydetachable individual cylinder heads, a crank case associated with saidcylinders, bridge means for engagement with said cylinder heads, andexpandable screw means, at least one of said screw means being common totwo adjacent cylinder heads with only said expandable screw meanstransmitting screw force by way of said bridge means upon two adjoiningcylinder heads and detachably connecting said two adjacent cylinderheads individually separable from the pertaining cylinders relative tosaid crank case.
 2. An arrangement according to claim 1, in which eachof said cylinder heads includes a plurality of bridge support points,and in which the vertical projection of the connecting line of twoadjacent bridge support points defines a chord with regard to thesurface center line of the annular joint surface between a cylinder headand the pertaining cylinder.
 3. An arrangement according to claim 1,which includes auxiliary supporting means arranged at the cylinders atthe ends of said engine and forming counter bearings for the respectiveadjacent bridge means.
 4. An arrangement according to claim 1, in whichsaid bridge means are provided with crowned engaging surfaces facing therespective adjacent cylinder head, and in which shim means areinterposed between said crowned engaging surfaces and the pertainingadjacent cylinder head surfaces.
 5. An arrangement according to claim 2,in which said bridge support points of said bridge means are located onthe upper surface of the pertaining cylinder head and are spaced fromsaid joint surface as far as possible.
 6. An arrangement according toclaim 2, in which said engine has gas inlet and outlet passage means,and in which said bridge support points are so located that the forcesintroduced into the cylinder heads by said bridge means pass through thewalls defining said inlet and outlet passage means.
 7. An arrangementaccording to claim 2, in which said engine has reinforcing wall means,and in which said bridge support points are so located that the forcesintroduced into the cylinder heads by said bridge means pass throughsaid reinforcing wall means.
 8. An arrangement according to claim 1, inwhich said cylinder heads and said cylinders have cast passage meanstherein for the passage of said expandable screw means.
 9. Anarrangement according to claim 1, which includes cylinder head covermeans mounted on said cylinder heads, and in which said expandable screwmeans with said bridge means are located within the maximum structuralheight of the engine including said cylinder head cover means.